Cylindrical rollers having a metal core and an elastomeric surface are used in a variety of applications, a typical application being in xerographic and electrophotographic duplicating machines. Such rolls are used to apply pressure and heat to a toner image on a substrate in order to fuse the image. In some instances, the rubber roll is covered with a polytetrafluoroethylene sleeve, and in other instances, the bare elastomer surface is desired.
The following United States patents relate to sleeved and unsleeved rubber rolls and methods and apparatus for making the same: U.S. Pat. Nos. 2,845,657; 2,864,130; 3,355,772; 3,380,120; 3,607,494; 3,613,168; 3,724,983; 3,912,901; 4,078,286; 4,083,092; 4,098,631; and 4,099,312.
A very important objective in the manufacture of rolls of the foregoing type is that the rolls have a near perfect concentricity of cylindrical surface as possible in which the diameter is constant along the axis thereof and the roll is free of surface irregularities. Heretofore, such precision has been possible primarily by injecting rubber into a seamless steel cylindrical mold having a precision formed inner surface. Such molds are, however, expensive to produce or acquire, and must be handled carefully in order to prevent damage to the molding surface. Also, in commercial scale production, a large number of such expensive molds are required because of the relatively long period required to cure rubber in a single mold, and also because various sizes of rolls must be produced.
In accordance with the conventional process for making a rubber covered roll, the core or shaft of the roll is usually coated with an adhesive or primer and is inserted into the metal mold and supported in concentric relation therewith. Uncured rubber is then injected into the space between the core and the mold. After the rubber is cured, the covered roll is withdrawn from the mold.
Under some conditions, a problem may arise wherein the injected rubber adheres to the mold surface, and a special operation is required to remove the roll, sometimes causing damage to the product. Such is particularly true with rubbers furnished in liquid form, such as certain silicone rubbers, which are injected under low pressure and then cured at room temperature or with the application of heat.